Amino acids with glucose

It is well known that the Maillard reaction in foods is initiated by the formation of colorless and tasteless intermediates, which preferentially are formed in low-moisture systems ( ,5.). In this way by reaction of glucose with amino acids fructose-amino acids are formed via Amadori rearrangement of the primary glucosyl-ami-no acids (1 ). Fructose-amino acids e.g. have been isolated from freeze-dried apricots and peaches ( 6,7,8j. Amadori compounds arising from aldoses and amino acids are formed during drying of foods of plant origin and can be easily detected by amino acid analysis (j>). 

The presence of furopyrazines demonstrates that Furaneol can react as an ot-dicarbonyl compound. Furopyrazines have also been found at trace levels after heating glucose with amino acids (J. Kunert-Kirchhoff and W. Baltes, Zeitschrift fur Lebensmittel- Untersuchung-Forschung, in press). After heating Furaneol alone to 180° C 17 degradation products have been identified. 

Several ideas have been presented in the literature on the formation process of humic substances in marine sediments. Abelson (1967) claimed that polymerization of unsaturated fatty acids in phytoplankters after their death accounts for the formation of kerogen in marine sediments. Abelson and Hare (1971), Hoering (1973), and Hedges (1976) studied reactions between carbohydrates and amino acids under laboratory conditions as a possible formation reaction of humic acid and humin in sediments. They prepared a number of artificial humic acids by reacting glucose with amino acids. The synthetic products resembled natural humic acid and humin. A comprehensive review was published by Abelson (1978). 

D-Fru-AA = Amadori compound of glucose with amino acid other than cysteine. 

The Mitsunobu condensation of 2,3,4,6-tetra-(9-acetyl-D-glucose with amino acid-derived 2-nitrobenzenesulfonamides led to formation of the protected... 

In the reaction of an aldose with an amino compound, such as the reaction of glucose with amino acids, three basic phases are recognised ... 

CCK is found in the digestive tract and the central and peripheral nervous systems. In the brain, CCK coexists with DA. In the peripheral nervous system, the two principal physiological actions of CCK are stimulation of gaU. bladder contraction and pancreatic enzyme secretion. CCK also stimulates glucose and amino acid transport, protein and DNA synthesis, and pancreatic hormone secretion. In the CNS, CCK induces hypothermia, analgesia, hyperglycemia, stimulation of pituitary hormone release, and a decrease in exploratory behavior. The CCK family of neuropeptides has been impHcated in anxiety and panic disorders, psychoses, satiety, and gastric acid and pancreatic enzyme secretions. 

A 0-9% salt solution is considered to be isotonic with blood. Other electrolytes present include bicarbonate ions (HCOj ) and small amounts of potassium, calcium, magnesium, phosphate, sulphate and organic acid ions. Included among the complex compounds and present in smaller amounts are phospholipids, cholesterols, natural fats, proteins, glucose and amino acids. Under normal conditions the extracellular body fluid is slightly alkaline with a pH of 7-4. ... 

Several types of cells are equipped with carrier proteins to transport essential nutrients such as glucose and amino acids that cannot cross the plasma membrane freely because of their hydrophilicity. Intestinal and renal epithelia have long been known to possess specialized Na+ cotransport processes for glucose [205], amino acids [206], and di- and tripeptides [207],... 

Some cells couple the pure transport forms discussed on p. 218—i.e., passive transport (1) and active transport (2)—and use this mechanism to take up metabolites. In secondary active transport (3), which is used for example by epithelial cells in the small intestine and kidney to take up glucose and amino acids, there is a symport (S) located on the luminal side of the membrane, which takes up the metabolite M together with an Na" ion. An ATP-dependent Na transporter (Na /lC ATPase see p. 350) on the other side keeps the intracellular Na+ concentration low and thus indirectly drives the uptake of M. Finally, a uniport (U) releases M into the blood. 

Proteins provide the body with amino acids, which are used for endogenous protein biosynthesis. Excess amino acids are broken down to provide energy (see p. 174). Most amino acids are glucogenic—I e they can be converted into glucose (see p. 180). 

Animal studies indicate that the primary toxic effect of uranium exposure is on the kidney, with particular damage to the proximal tubules. Functionally, this may result in increased excretion of glucose and amino acids. Structurally the necrosis of tubular epithelium leads to formation of cellular casts in the urine. If exposure is insufficient to cause death from renal failure, the mbular lesion is reversible with epithelial regeneration. Although bone is the other major site of deposition, there is no evidence of toxic or radiocarcinogenic effects to bone or bone marrow from experimental studies. ... 

It is to be noted that similar compounds and degradation products tend to interfere with the signal of the analyzed compounds. The severest interferences were observed for catechol and resorcinol, whereas cresols and chlorophenols had only little effect. Common substrates, such as glucose and amino acids, produced only low signals. A Rhodococcus PI, which has been isolated from sediment of the river Saale, in particular had a very high sensitivity to phenol and... 

The pancreas responds to elevated levels of glucose and amino acids with an increased secretion of insulin and a drop in the release of glucagon by the islets of Langerhans. The elevated insulin to glucagon ratio and the ready availability of circulating substrates make the two to four hours after ingestion of a meal into an anabolic period. 

Glucose reacts non-enzymatically with amino acids and proteins, including hemoglobin, egg-white proteins and serum albumin. For example, if glucose is not removed prior to drying, dried egg whites slowly turn brown and develop off-flavors and odors. What do you propose as the most likely first step in the non-enzymatic glucose-protein chemical reaction How can the first product transform spontaneously into a ketose derivative ... 

As mentioned, AMP-PNP or ADP in the presence of glucose will bind only to the BII crystals at a site between the two subunits. Nucleotides bound at this site appear to be in a fully extended conformation (73). ATP analogs bound at this site make contact with amino acid residues from both subunits. The y-phosphate of ATP bound at this site is 20 A from the 6-hydroxyl of bound glucose on one subunit and 30 A from the glucose on the other subunit (73). It has been proposed that this site is an allosteric regulatory site for hexokinase and not the substrate site for ATP where phosphoryl transfer occurs (73). 

Oxidation, in combination with the tricarboxylic acid cycle and respiratory chain, provides more energy per carbon atom than any other energy source, such as glucose and amino acids. The equations for the complete oxidation of palmitoyl-CoA are shown in table 18.1. Equation (1) in the table shows the oxidation of palmitoyl-CoA by the enzymes of j8 oxidation. Each of the products of equation (1) is further oxidized by the respiratory chain, equations (2) and (3), or by the tricarboxylic acid cycle and the respiratory chain, equation (4). When the reactions of equations (l)-(4) are summed, the result is equation (5). Hence, complete oxidation of one molecule of palmitoyl-CoA yields 108 ATP + 16C02 + 123 H20 and CoA. The water generated by /3 oxidation seems almost incidental to this process, but is crucial in several animal species. For example, the oxidation of fatty acids is used as a major source of H20 by the killer... 

The barrier to paracellular diffusion potentially isolates the brain from many essential polar nutrients such as glucose and amino acids that are required for metabolism and, therefore, the BBB endothelium must contain a number of specific solute carriers (transporters) to supply the CNS with its requirements for these substances. The formation of tight junctions essentially confers on the BBB the properties of a continuous cell membrane, both in terms of the diffusional characteristics imposed by the lipid bilayer, and the directionality and properties of the specific transport proteins, and solute carriers (SLC) that are present in the cell membrane. Examples of BBB solute carriers (SLC transporters) are listed in Table 27.2. 

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